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Pressure in tank

  • Thread starter foo9008
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  • #1
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Homework Statement


in this question , the author stated that the P1 = P atm , but at point 1 , the gas tank is not open to the atmosphere, it is a closed tank . so , is the author wrong ? again , at point 2 , the tank isn't open to atmosphere, why it is P2= P atm ?

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Answers and Replies

  • #2
gneill
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Why might the two pressures be P atm? Can you think of any reason? How does the small diameter hose reach the liquids?
 
  • #3
678
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Why might the two pressures be P atm? Can you think of any reason? How does the small diameter hose reach the liquids?
i dont think P1 and P2 = P atm .....
 
  • #4
gneill
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i dont think P1 and P2 = P atm .....
I understand that. But can you think of any way that they could?
 
  • #5
678
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I understand that. But can you think of any way that they could?
for P1 = P2 = P atm , the tank is not closed?
 
  • #6
gneill
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for P1 = P2 = P atm , the tank is not closed?
Correct. How does the hose enter each tank?

upload_2016-4-8_10-59-47.png
 
  • #7
678
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Correct. How does the hose enter each tank?

View attachment 98796
at point 1 , it is immersed in the gas tank , while the point 2 is at the hole only , not completely immersed . What are you trying to tell ?
 
  • #8
gneill
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at point 1 , it is immersed in the gas tank , while the point 2 is at the hole only , not completely immersed . What are you trying to tell ?
I'm pointing out that neither tank is sealed. Both are open to the atmosphere through their filling apertures. The siphon hose does not make an air-tight seal at either opening.
 
  • #9
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I'm pointing out that neither tank is sealed. Both are open to the atmosphere through their filling apertures. The siphon hose does not make an air-tight seal at either opening.
if that is air-tight selaed , then the pressure acting would not be P atm anymore , am i right ?
 
  • #10
gneill
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if that is air-tight selaed , then the pressure acting would not be P atm anymore , am i right ?
Sure. It might start out at P atm at the moment a seal was made though.

But there is no seal mentioned in the problem statement. The assumption is that, as in the real-life situation for siphoning gas in this manner, the hose fits loosely through the gas cap opening and down into the liquid.
 

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